Siam is a pretty interesting civ when playing the new expansion Brave New World. Their unique ability, which grants them an increase in culture, food, and faith, means the Siamese are primarily designed for a diplomatic victory.

Their unique building, the Wat, grants three extra culture to universities and their unique unit, Naresuan's Elephants, are one of the strongest in the medieval era.

Naturally, a diplomacy victory seems the most attractive, however, with Siam's unique buildings and units, just about any method of winning is on the table.